The investigators want to show whether clonidin has an procoagulatoric effect on thrombozytes of patients under double anticoagulaotirc treatment with ASS and clopidogrel. The investigators will use a flowcytometric assay to determine activation of thrombozytes when they come into contact with clonidine in vitro as well as Multiplate analyses to determine activation of thrombozytes, either thrombin.induced aggregation, ADP-induced aggregation or arachidonic acid-induced aggregation of thrombozytes.